Note for Computer Organistaion and Operating System - COOS By JNTU Heroes

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COMPUTER ORGANIZATION AND OPERATING SYSTEMS III B. Tech I semester (JNTUH-R13) COMPUTER SCIENCE AND ENGINEERING 1

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UNIT-1 BASIC STRUCTURE OF COMPUTERS Contents:  Computer Types  Functional Unit  Basic Operational concepts  Bus structures  Software performance  Multiprocessors and multi computers  Data Representation  Fixed point Representation  Floating- point Representation 2

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Unit- I Basic Structure of Computers Computer Architecture in general covers three aspects of computer design namely: Computer Hardware, Instruction set Architecture and Computer Organization. Computer hardware consists of electronic circuits, displays, magnetic and optical storage media and communication facilities. Instruction set Architecture is programmer visible machine interface such as instruction set, registers, memory organization and exception handling. Two main approaches are mainly CISC (Complex Instruction Set Computer) and RISC (Reduced Instruction Set Computer) Computer Organization includes the high level aspects of a design, such as memory system, the bus structure and the design of the internal CPU. Computer Types Computer is a fast electronic calculating machine which accepts digital input, processes it according to the internally stored instructions (Programs) and produces the result on the output device. The internal operation of the computer can be as depicted in the figure below: Figure 1: Fetch, Decode and Execute steps in a Computer System 3

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The computers can be classified into various categories as given below:  Micro Computer  Laptop Computer  Work Station  Super Computer  Main Frame  Hand Held  Multi core Micro Computer: A personal computer; designed to meet the computer needs of an individual. Provides access to a wide variety of computing applications, such as word processing, photo editing, e-mail, and internet. Laptop Computer: A portable, compact computer that can run on power supply or a battery unit. All components are integrated as one compact unit. It is generally more expensive than a comparable desktop. It is also called a Notebook. Work Station: Powerful desktop computer designed for specialized tasks. Generally used for tasks that requires a lot of processing speed. Can also be an ordinary personal computer attached to a LAN (local area network). Super Computer: A computer that is considered to be fastest in the world. Used to execute tasks that would take lot of time for other computers. For Ex: Modeling weather systems, genome sequence, etc (Refer site: http://www.top500.org/) Main Frame: Large expensive computer capable of simultaneously processing data for hundreds or thousands of users. Used to store, manage, and process large amounts of data that need to be reliable, secure, and centralized. Hand Held: It is also called a PDA (Personal Digital Assistant). A computer that fits into a pocket, runs on batteries, and is used while holding the unit in your hand. Typically used as an appointment book, address book, calculator and notepad. Multi Core: Have Multiple Cores – parallel computing platforms. Many Cores or computing elements in a single chip. Typical Examples: Sony Play station, Core 2 Duo, i3, i7 etc. 4